The Southern California Regional Gamma Knife Center (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Renovation installation and operation agreement period			14 years
Neuro Partners LLC and CGK Condensed Income Statement Information [Abstract]
Patient revenue	$ 0	$ 469,000	$ 0	$ 1,064,000
USNC's equity in income (loss)	19,000	6,000	12,000	(15,000)
CGK [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage (in hundredths)	39.00%		39.00%
Neuro Partners LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage (in hundredths)	20.00%		20.00%
Neuro Partners LLC and CGK [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of guarantee obligations (in hundredths)			20.00%
Period of lease with respect to gamma knife equipment and certain leasehold improvements			7 years
Outstanding balance on the lease obligations	2,606,000		2,606,000
Option to purchase the gamma knife	490,000		490,000
Neuro Partners LLC and CGK Condensed Income Statement Information [Abstract]
Patient revenue	245,000	269,000	603,000	516,000
Rental income	222,000	222,000	444,000	444,000
Net sales	467,000	491,000	1,047,000	960,000
Net income (loss)	(66,000)	159,000	(3,000)	27,000
USNC's equity in income (loss)	(28,000)	32,000	(6,000)	10,000
Equity Method Investment Summarized Financial Information Balance Sheet [Abstract]
Current assets	547,000		547,000		468,000
Noncurrent assets	1,943,000		1,943,000		2,261,000
Total assets	2,490,000		2,490,000		2,729,000
Current liabilities	1,112,000		1,112,000		442,000
Noncurrent liabilities	1,990,000		1,990,000		2,896,000
Equity	(612,000)		(612,000)		(609,000)
Total liabilities and equity	$ 2,490,000		$ 2,490,000		$ 2,729,000